In view of the wide variations that can occur in network usage, and in particular in cells covering a geographical location providing a facility such as a sports stadium which can cause the total number of mobile phone users to vary widely, it can prove important to move network-traffic between cells and frequencies.
Therefore during busy hours such as those that might be experienced within the cell during a sporting event, it is conceivable that the network will become overloaded and will therefore be required to push traffic into a cell offering a less-loaded frequency layer.
Prior to performing such a handover to the desired cell, it is necessary for the network to initiate inter-frequency measurements within the mobile radio communications device handset so as to identify the most appropriate target cell and frequency.
The provision of such inter-frequency measurements that are then provided in return from the mobile radio communications device handset to the network, assists the Radio Resources Management (RRM) layer within the network to balance the signalling load across the available frequencies.
Without such inter-frequency measurements, the network would not be able to use its resources efficiently and, likewise, the mobile radio communications device would be more likely to suffer from interference insofar as it could not be assigned to a new frequency. Yet further, if greater interference is experienced by a device handset that handset is then likely to initiate transmission at a higher power which would lead to joint disadvantages of greater power consumption, and thus shorter battery life, and the likely generation of greater interference for other users.
It should however be appreciated that the performance of inter-frequency measurements consumes battery power, and so the trigger of inter-frequency measurements should be carefully controlled.
Indeed, in order to save power while the mobile radio communications device is in the IDLE/CELL PCH and URA-PCH states, the device generally does not perform inter-frequency measurements such that the response to any incoming paging signals is generally made without the inter-frequency measurements.
Further, current RRM specifications dictate that a network may request that an already-connected mobile radio communications device perform inter-frequency measurements so as to lead to a frequency-handover in order to maintain minimal interference level as discussed above. However, it should be appreciated that such a method requires the use of “compressed mode” functionality which is generally available only as an optional capability within the mobile radio communications devices. This can advantageously cause interruption to the service availability and which can prove to be frustrating for the user.